This application is for the Glaucoma Laser Trial Follow Study (GLTFS), a prospective, observational followup study of patients treated for primary open-angle glaucoma (POAG) and for analyses of GLTFS and GLT data. Participants in the GLTFS will be recruited from the 271 patients who enrolled in the Glaucoma Laser Trial (GLT); the study population is estimated to be 261. The objectives of the GLTFS are: to extend followup on GLT patients for an additional 3 years to provide 5- 8 years of data on progression of treated POAG; to analyze the GLTFS data with the GLT data to produce publishable manuscripts describing the course of treated POAG; and to continue the analysis of GLT treatment effects data to produce publishable manuscripts not subsumed under the GLT. The existing GLT organizational structure which currently supports manuscript production will be maintained in the GLTFS. Patients in the GLTFS will be seen annually for 3 years. Visit procedures will include refraction, visual acuity measurement, tonometry, perimetry, funduscopy, disc stereophotography and gonioscopy. Information will be obtained by the patient's interim and medical history. Treatment for POAG will be managed by the patient's personal ophthalmologist.